How is pregnancy week calculated?

Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception. Week 1 and 2 are before conception — this is the standard medical convention. A full-term pregnancy is 40 weeks (280 days).

What are the three trimesters?

First trimester: weeks 1–12. Second: weeks 13–27. Third: weeks 28 until birth. Each trimester has different developmental milestones and screening tests, so knowing your week helps you track what to expect.

Can I use my due date instead of LMP?

Yes. Select "Due date" and enter the date your doctor gave you. The tracker will compute your LMP (due date minus 280 days) and show the same current week, trimester and progress.

Is my data sent to any server?

No. Everything runs 100% locally in your browser. Your pregnancy dates never leave your device.

Why do doctors count from LMP if I wasn't pregnant then?

Because the exact conception date is usually unknown. LMP is a universal, easy-to-remember reference point. The two weeks before conception are included in the 40-week count, which is why a full-term pregnancy is roughly 38 weeks from conception.

How accurate are the trimester boundaries?

Trimester boundaries are conventions, not sharp biological transitions. Some sources define the second trimester as weeks 13–27, others as 14–27. In practice, the boundaries matter mostly for medical scheduling (screening tests, viability windows), not for daily pregnancy experience.

Pregnancy Week Tracker

Track your pregnancy week by week. Enter your last period or due date and see your current week, trimester, progress percentage and days until birth. Uses the medical convention of counting from the last menstrual period, not conception.

How to use

Choose your method

Select Last menstrual period or Due date.

Enter the date

Type the first day of your last period or your estimated due date.

Read your progress

See your current week, trimester, progress percentage and days until birth.

Features

Current pregnancy week

See exactly which week of pregnancy you are in.

Trimester indicator

Know whether you are in the first, second or third trimester.

Progress percentage

See how far along you are as a percentage of the full 40 weeks.

Days until due date

See exactly how many days remain until your due date.

Due date from LMP or EDD

Calculate from either your last period or your doctor's due date.

Common use cases

Track which week of pregnancy you are in
See how many days remain until your due date
Understand which trimester you are in
Monitor pregnancy progress over time

Frequently Asked Questions

Related tools

Pregnancy Due Date Calculator

Menstrual Cycle Calculator

Calorie Calculator

Age Calculator